by: Schmoll, J. T.; Harrison, S. K.; Regnier, E.
E.; Bennett, M. A.
A greenhouse study was conducted to determine the effects of sublethal dicamba concentrations in the nutrient media on hydroponically grown tomato plants. One part of the study was a range-finding bioassay conducted to determine the logarithmic dose response of tomatoes to dicamba in the nutrient media. The other part of the study was a determination of long term effects of acute exposure to sublethal dicamba on tomato growth and initial fruit yield. Seedlings at the 4- to 6-leaf stages were transplanted into a hydroponic system containing nutrient solutions mixed with dicamba. Tomato leaf area was the most sensitive vegetative growth parameter measured in response to dicamba concentrations ranging from 0 to 22 µg/litre. Leaf area was reduced by 31 and 76%, and specific leaf weights (a relative measure of leaf thickness (g/cm2)) increased by 26 and 121%, after a 30-day exposure to dicamba concentrations of 2.2 and 22 µg/litre, respectively. In long-term experiments conducted until plants produced first ripe fruit, regression analysis indicated leaf area reductions of 8 and 66% from initial dicamba concentrations of 1 and 10 µg/litre, respectively. Reductions in total fruit fresh weight were highly correlated (r=0.93) with leaf area reductions caused by dicamba. A hyperbolic regression model gave predicted losses of 6% in fruit fresh weight per plant at 1 µg/litre dicamba and 73% at 10 µg/litre
dicamba (r2=0.87). Results generally indicated that the level
of dicamba in the nutrient media of hydroponically grown tomatoes that produced
no observable effect was ≤1 µg/litre.
A greenhouse study was conducted to determine the effects of sublethal dicamba concentrations in the nutrient media on hydroponically grown tomato plants. One part of the study was a range-finding bioassay conducted to determine the logarithmic dose response of tomatoes to dicamba in the nutrient media. The other part of the study was a determination of long term effects of acute exposure to sublethal dicamba on tomato growth and initial fruit yield. Seedlings at the 4- to 6-leaf stages were transplanted into a hydroponic system containing nutrient solutions mixed with dicamba. Tomato leaf area was the most sensitive vegetative growth parameter measured in response to dicamba concentrations ranging from 0 to 22 µg/litre. Leaf area was reduced by 31 and 76%, and specific leaf weights (a relative measure of leaf thickness (g/cm2)) increased by 26 and 121%, after a 30-day exposure to dicamba concentrations of 2.2 and 22 µg/litre, respectively. In long-term experiments conducted until plants produced first ripe fruit, regression analysis indicated leaf area reductions of 8 and 66% from initial dicamba concentrations of 1 and 10 µg/litre, respectively. Reductions in total fruit fresh weight were highly correlated (r=0.93) with leaf area reductions caused by dicamba. A hyperbolic regression model gave predicted losses of 6% in fruit fresh weight per plant at 1 µg/litre dicamba and 73% at 10 µg/litre
dicamba (r2=0.87). Results generally indicated that the level
of dicamba in the nutrient media of hydroponically grown tomatoes that produced
no observable effect was ≤1 µg/litre.Yangzhou pioneer chemical CO.,LTD
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